Virtual reality or virtual realities (VR) (also sometimes interchangeably referred to as immersive multimedia or computer-simulated reality) describes a simulated environment designed to provide a user with an interactive sensory experience that seeks to replicate the sensory experience of the user's physical presence in an artificial environment, such as a reality-based environment or a non-reality-based environment, such as a video game. A virtual reality may include audio and haptic components, in addition to a visual component.
The visual component of a virtual reality may be displayed either on a computer screen or with a stereoscopic head-mounted display (HMD), such as the Rift, a virtual reality head-mounted display headset developed by Oculus VR of Seattle, Wash. Some conventional HMDs simply project an image or symbology on a wearer's visor or reticle. The projected image is not slaved to the real world (i.e., the image does not change based on the wearer's head position). Other HMDs incorporate a positioning system that tracks the wearer's head position and angle, so that the picture or symbology projected by the display is congruent with the outside world using see-through imagery. Head-mounted displays may also be used with tracking sensors that allow changes of angle and orientation of the wearer to be recorded. When such data is available to the system providing the virtual reality environment, it can be used to generate a display that corresponds to the wearer's the angle-of-look at the particular time. This allows the wearer to “look around” a virtual reality environment simply by moving the head without the need for a separate controller to change the angle of the imagery. Wireless-based systems allow the wearer to move about within the tracking limits of the system. Appropriately placed sensors may also allow the virtual reality system to track the HMD wearer's hand movements to allow natural interaction with content and a convenient game-play mechanism
However, a condition referred to as virtual reality sickness (also known as cybersickness) may occur when a user is exposed to a virtual reality environment. Virtual reality sickness can cause symptoms that are similar to the symptoms caused by motion sickness, such as general discomfort, headache, stomach awareness, nausea, vomiting, pallor, sweating, fatigue, drowsiness, disorientation, and apathy. Other symptoms may include postural instability and retching. Virtual reality sickness is distinguishable from motion sickness because it can be caused by the visually-induced perception of self-motion; real self-motion is not needed.
A significant aggravating factor in virtual reality sickness is whether the visual component of the virtual reality being experienced by the user represents is tied to the user's self-motion. In other words, if a user is “seeing” a virtual reality where the viewing-user's perspective is controlled by another user (or a computer), the viewing-user is more likely to develop symptoms of virtual reality sickness (this may be analogous to the anecdotally common real-world scenario of a passenger in a car developing symptoms of motion sickness while the driver of the car does not). For example, if the user controlling the perspective may unexpectedly swivel his or her head from side to side and the viewing-user is not expecting that sudden shift in perspective, virtual reality sickness may result.
Some conventional software applications, particularly video games where multiple players interact with a video game program within the same video game session, allow non-participating, “spectator,” users to passively interact with the game session, e.g. by selectively navigating around the game session's environment, while the game session is ongoing.
Some conventional video games (and game engines) may include a static replay creation feature that records game-state data corresponding to a game session and allows a user to view a replay video of the game session within the video game. Third party tools that capture the display data generated during a game session and stores it in a video format for later playback are also known. Video-based replays created by the third party tools support sharing via online playback and commonly available video players but require much more storage space than replays created with in the context of the video game itself.
These exiting tools illustrate a recognition that video game users may desire to record a game session in order to replay at a later time or to distribute for others replay, e.g. for entertainment purposes, similar to viewing a recorded sporting event. Game replays may also be used in the prevention and detection of cheating or to develop skill at a video game, e.g. by watching better players and observing their techniques. Video game replays may also be used to raise stature in a particular game's user community, e.g. to establish rankings among players or to settle disputes. Video game replays are also used to produce replay reviews, i.e. a review of a game replay by an experienced player to determine what can be done to improve and expand upon the original player's skill.
Because many conventional video game replay techniques are designed to recreate the player's perspective, they cannot be used in a virtual reality implementation because a user experiencing a replay of another user's virtual reality perspective may be at a heightened risk of developing virtual reality sickness. Such concerns over virtual reality sickness may be a major barrier to applying conventional video game replay techniques to virtual reality video games.
Additionally, many virtual reality-based video games create expansive and detailed virtual environments which may not be sufficiently explorable using conventional player-perspective video replay techniques, such as static video capture.